The present invention relates to a vehicle suspension apparatus which can reduce roll back of a vehicle body when the steering wheel is quickly returned to the neutral position during vehicle travel.
In order to reduce rolling of a vehicle making a turn, the present applicant previously proposed a vehicle suspension apparatus comprising: fluid spring chambers arranged for suspension units supporting respective wheels of the vehicle; fluid supply means for supplying a fluid to the fluid spring chambers through corresponding supply control valve means; fluid exhaust means for exhausting the fluid from the fluid spring chambers through corresponding exhaust control valve means; communicating means for communicating the fluid spring chambers of the left suspension units with those of the right suspension units through communication control valve means; steering state detecting means for detecting the steering state of the steering wheel; communication control means for supplying a control signal to the communicating means so as to open the communication control valve means when the steering angle is detected to fall within a preset neutral range by the steering state detecting means and for supplying a control signal to the communication means so as to close the communication control valve means when the steering angle is detected to fall outside the neutral range by the steering state detecting means; and roll control means for producing a control signal for suppling a preset amount of a fluid to the fluid spring chambers of the contracted suspension units and for exhausting a preset amount of the fluid from the fluid spring chambers of the stretched suspension units when the steering state detecting means and vehicle velocity detecting means detect a factor which causes rolling of the vehicle body.
However, the above apparatus is subject to the following problem. Assume a state wherein the steering wheel is quickly operated in order to avoid an obstacle on the road during high-speed travel and the steering wheel is then quickly returned to the neutral position. In this case, while the vehicle body quickly returns from the roll state to the neutral state, the communication control means opens the communication control valve means of the communicating means. Then, the roll rigidity of the vehicle body is reduced. When this occurs, the vehicle body rolls to the opposite side exceeding the neutral position, thereby causing roll back of the vehicle body.